Lots of gardeners add used coffee grounds to their gardens to improve the texture of the soil. Several readers of this site have suggested that coffee grounds spread around the soil at the base of lilies might also provide an environmentally friendly way to deter lily leaf beetles. While this sounded entirely plausible (insects using their sense of smell to find their host plants might be repelled by any number of odoriferous substances), I always wondered whether the gardeners who swore by this method had actually reduced the populations of the beetle by other means, such as diligently hand picking the eggs, larvae and adults. A couple of days ago, I finally got around to putting the coffee solution to the test.

Because we have so few lily beetles in our test plots (thanks to our very effective biocontrol agent Tetrastichus setifer) I was only able to find eight adult lily beetles to test for their response to coffee. With so few beetles, I didn't want to risk losing any in an open-garden experiment, so I set up choice tests in plastic bins. Each bin contained a segment of a lily stem "planted" in about two cups of either soil from my garden or used coffee grounds. A beetle was placed in the middle, as shown below:

Five beetles headed straight for the coffee; three ended up on the lily planted in garden soil. When a beetle encountered the coffee, it wasn't in the least deterred, but climbed right up on the mound of grounds and walked across it to the plant.

One reader suggested testing fresh coffee. He has a point. The coffee grounds used in my experiment had already had most of the caffeine extracted to make my morning cuppa joe over the past few weeks. Caffeine may, in fact, act as a natural insecticide, so freshly ground coffee might be a much more effective deterrent against incoming beetles. On the other hand, fresh coffee would be a very expensive way to keep lily beetles out of your garden!

These cocoons were made by parasitized lily beetle larvae last summer. They have been overwintering in cold storage. Each cocoon contains about a dozen tiny wasps. Now that the lily beetle adults are starting to mate and lay eggs, it's time to wake up the wasps so they can get to work doing what they do best!

Darlene from Florida sends this picture of the air-potato beetle, Lilioceris cheni, which was introduced a few years ago to combat the invasive alien air-potato vine. Looks like this biocontrol beetle is doing a great job! Of course, destroying plants runs in the family. If only the lilies in our gardens were invasive alien plants we wanted to be rid of!﻿

Today we revisited a site in the Gatineau Park where Master's student Chelsea Kealey found three lily leaf beetle eggs on twistedstalk Streptopus lanceolatus in 2013 (which we had mis-identified as Streptopus amplexifolius). I thought this 2013 observation might simply be the result of one lost female dumping eggs on the closest thing to a lily it could find. It turns out there is an established lily beetle population on twistedstalk in the Park. Today we found several plants with eggs or larvae, and one female laying eggs.

New Master's student Chelsey Blackman (below) will be studying whether our biocontrol agent Tetrastichus setifer can find the lily beetle when it is on plants other than lilies. Herbivores expanding their host range by moving onto novel host plants can escape their natural enemies, which are sometimes hard-wired to search for the herbivore on the original plant. Will the lily leaf beetle evade Tetrastichus setifer by moving into the forest and onto twisted stalk? Stay tuned...

The Canada lily (Lilium canadense) is one of eastern Canada's most beautiful wildflowers. Its range extends into the southern US, and it is listed as threatened or vulnerable in several states. As the lily leaf beetle expands its range, it is putting populations of Canada lily at further risk.

Last week, doctoral students from the University of Montreal released the biocontrol agent Tetrastichus setifer in a population of Canada lily in Quebec that was under heavy attack from the beetle. Upon release, the agent, a tiny wasp, got right to work parasitizing beetle larvae:

Hopefully, the wasp will become established and help to control the beetle so that it does not become abundant enough to kill the lilies. Back home in our Ottawa test gardens, parasitism rates this year appear to be very close to 100%. We're even worried about not having enough lily beetles next year...imagine that!

I spent a couple of hours today at the Burnt Lands Alvar, north of Almonte, ON, looking for lily beetles on the wood lilies there. Wood lily, Lilium philadelphicum, is a good food plant for the lily beetle in the lab, but does not seem to be attacked in nature. I have been looking for beetles on the plants at the Burnt Lands for several years now and have not even seen any damage that resembles lily beetle feeding. It is a mystery why the lily beetles have not colonized this large population of native lilies.

Wood lilies rival any variety of Asiatic garden lily for their beauty:

The population of lilies at the Burnt Lands seemed especially healthy this year, with hundreds of individuals in bloom. Many stems had two, three, four and even up to five flowers.

Also in bloom today were wild roses (Rosa acicularis)....

...as well as starry false Solomon's seal, which I see from the USDA Plants database I need to start calling starry false lily of the valley (Maianthemum stellata; used to be Smilacina stellata):

It was good to see that certain parcels of the alvar are now a Provincial Park, and are protected by a barrier to vehicles. Hopefully, this will help put a stop to the poaching of wildflowers. I did notice some fresh ATV tracks though, so people are still managing to abuse this sensitive natural area despite the barriers.

The biocontrol agent, Tetrastichus setifer, is out and about in our experimental lily garden. Ace photographer Andrea Brauner caught this female doing what T. setifer does best:

The experimental garden has several lily varieties, of which the Asiatic "Tiny nugget" seems especially susceptible. While this is good for us, since we need a healthy lily beetle population to keep the wasps happy, you might want to avoid this particular hybrid.

These heavily damaged plants do not mean that T. setifer is ineffective. Last year, the waspskilled over 80% of the larvae in the garden, so to make sure our beetle population stays high, we supplement with beetles found in other gardens.﻿

Our biological control program at the Experimental Farm in Ottawa has been a great success. The tiny wasp Tetrastichus setifer (shown below) has become established in our experimental garden and is quite abundant. This past week, I saw nearly as many wasps as beetle larvae on our lilies.

Additional wasps in parasitized lily beetle cocoons from last year have been removed from cold storage. If their survival was good, then we expect to have a surplus of wasps. We would like to find additional release sites for these wasps. We will give priority to sites that meet the following criteria:

large number (50+) lily plants

in neighbourhoods where other gardeners grow lilies

not exposed to pesticides

gardener must agree to allow lily beetles to feed and develop so that they may become parasitized

gardener must agree to follow-up collection of larvae to assess success of release

The following metropolitan areas will be given priority (if your city is not on the list, we probably already have a contact there):

Edmonton

Winnipeg

Toronto

Halifax

If you meet the criteria and would like your garden to become a release site, please email me: Naomi_Cappuccino at carleton.ca.

Help us focus our biological control efforts on protecting populations of Canada lily (Lilium canadense), Michigan lily (Lilium michiganense),Turk’s cap lily (Lilium superbum) and wood lily (Lilium philadelphicum). These species are all endangered or threatened in certain states/provinces. All four species occur within the range of the lily leaf beetle. There has been good documentation of lily leaf beetle on Canada lily in Quebec, and the absence of the beetle on wood lily in Ontario (1). However, as the beetle spreads through Southern Ontario, reports of lily leaf beetle attacking populations of Michigan lily are becoming more common. We need to document the extent of this invasion, start monitoring lily populations and eventually introduce biological control agents at these sites. Turk’s cap lily does not occur in Canada, but is present in several northeastern US states where the lily leaf beetle is a serious garden pest. Please let us know if you see beetles on this species. A great site for ranges, photos and legal status of native lily species is the UDSA Plants database. Click on “subordinate taxa” for range maps and information on individual Lilium species. You can use our form to report your observations.

Meadow voles have apparently been very abundant here on the Central Experimental Farm this winter. What used to be my experimental lily garden is a mess of trails and tunnels and a big cache of partially eaten bulbs.

The silver lining to this vole outbreak is that we have had the privilege of watching snowy owls hunt them over the past month!